The office was subject to daily protests following Belfast City Council's December 3 vote to alter the protocol for flying the union flag over City Hall.

Ms Long received death threats over her perceived role in the process and was warned to stay away from the office.

Mr Lyttle condemned those responsible for the alert: "Whether a hoax or viable device, this is a serious and reckless act.

"There are homes, businesses and a children's play park in the area. This is an attack on the community and democratically elected representatives.

"This act has served no cause or purpose other than to endanger and disrupt people going about their daily business and should be condemned by all.

"This does not represent the majority of people who support a shared and better future for east Belfast, which we will continue to work to deliver."

He said the incident will not deter him or his colleagues from serving their constituents.

His sentiments were echoed by Ms Long, who used social media to get her message across, writing on her Facebook page: "Our office is there to serve people. We'll continue to do it.

"We won't allow the minority, who have nothing to offer beyond threats, intimidation and violence stop us doing our duty."

A separate hoax alert caused anguish among parents of a primary school in east Belfast on October 2.

Police were called to Elmgrove Primary School on the Beersbridge Road after a warning was made to the school at 8.22am.

A letter to parents stated the school initiated its "critical incident procedures". Neither teachers nor pupils were evacuated from the building.

A PSNI spokesperson said: "Police were assigned to the school and with the assistance of staff carried out an initial search of the school. A police dog assisted in the search of the premises.

After 90 minutes nothing suspicious was found and the report was declared as a hoax.

"The safety of the pupils and staff in the building were always at the forefront of all actions taken by police and this was constantly under review during the incident. Police wanted to ensure that there was as little disruption and fear caused to the children as possible while any risk was carefully considered by all officers involved.

Anyone with any information about this incident is asked to contact Strandtown Police Station on 0845 600 8000